Abstract: Study of self-adjustable mechanisms without overconstraint, which are high efficiency and stability and low cost, is the most important aspect of robust design based on the uncertainty of planar constraints. Mechanism of self-adjustment is analyzed for planar crank-rocker mechanism without overconstraint, and self-adjustment conditions of the crank-rocker mechanism are derived from the condition of self-locking in prismatic pair. With this understanding, a method, which can be used to analyze performance of self-adjustment for the crank-rocker mechanism, is proposed and allowable error angles that the mechanism can self-adjust are found. Some conclusions and rules, which can be applied to synthesizing for the self-adjustable mechanisms and determining for shape-position tolerances of kinematic-pair elements and axes, are obtained. Thereby, the theoretic foundation is provided for designing self-adjustable machines scientifically, and not experientially.

Key words: Allowable errors, Crank-rocker mechanism, Overconstraint, Self-adjustable structures, Self-adjustment